The present invention relates to a network communication monitoring system for monitoring continuation and blockade of a network in the network using an IP network, a network communication monitoring method, a central apparatus, a relay unit, and a memory product for storing a computer program.
In recent years, in accordance with a rapid progress of a communication technology, various services using an IP network has been provided. Then, in order to realize a stable supply of a service, it is required to monitor the state of the IP network. For example, the monitoring apparatus transmits a request packet by a Ping command (a communication monitoring command) to a terminal device to which the monitoring system is connected via the network and the monitoring apparatus can specify the place where a network failure occurs and the terminal device or the like where the failure occurs depending on whether or not it receives a reply packet to the request packet, so that it is possible to attempt an early recovery of the failure (refer to Japanese Patent Application Laid-Open No. 2002-111665).
FIG. 1 is a block diagram showing the structure of a monitoring system of a conventional network. As shown in FIG. 1, a plurality of routers (relay units) 2, 2, . . . is connected to a monitoring apparatus (a central apparatus) 1, and the routers (central apparatuses) 2, 2, . . . are connected thereto in a hierarchical fashion. To the routers 2, 2, . . . at the lowest layer, one or plural terminal devices 3, 3, . . . having the same network classes are connected.
The monitoring apparatus 1 issues a Ping command designating a destination information of the terminal devices 3, 3, . . . which are monitoring objects, for example, an IP address. In the case that the monitoring apparatus 1 issues the Ping command, the monitoring apparatus 1 transmits a request packet to the designated destination and each of the terminal devices 3 receives the request packet. In the case that the terminal device 3 receives the request packet, the terminal device 3 generates a reply packet and returns it to the monitoring apparatus 1. When the monitoring apparatus 1 receives the reply packet, the monitoring apparatus 1 determines that the network with the terminal device 3 which returns this reply packet normally functions and when the monitoring apparatus 1 does not receive the reply packet, the monitoring apparatus 1 determines that a failure occurs in the network with the terminal device 3 which does not return the reply packet.